JPH0320655A - Apparatus for detecting abnormality of oxygen sensor - Google Patents

Abstract

PURPOSE:To accurately detect the abnormality of an oxygen sensor by judging the abnormality of the oxygen sensor in such a case that the output signal of the oxygen sensor is equal to or more than a predetermined threshold value or equal to or less than said threshold value when an air/fuel ratio is set to a lean or rich state. CONSTITUTION:The air/fuel ratio of the fuel mixed air supplied to an internal combustion engine M1 is subjected to open loop control by an air/fuel ratio setting means M3 to be set to a lean or rich state. In such a case that the output signal of an oxygen sensor 2 becomes a predetermined threshold value or more when the air/fuel ratio is set to the lean state, it is judged that the sensor M2 is a deteriorated sensor much in an Nox discharge amount. In such a case that the output signal of the sensor 2 becomes the predetermined threshold value or less when the air/fuel ratio is set to the rich state, the sensor 2 is judged to be a deteriorated sensor much in a CO discharge amount. By this method, the abnormality of the sensor 2 can be accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an abnormality detection device for an oxygen sensor that measures the oxygen concentration of exhaust gas from an internal combustion engine or the like.

[Prior Art] Conventionally, in order to reduce emissions in the exhaust gas of an internal combustion engine, the air-fuel ratio of the fuel mixture to be supplied to the internal combustion engine has been adjusted based on the output signal of an oxygen sensor attached to the exhaust system of the internal combustion engine. controlled.

That is, as shown in FIG. 12, air-fuel ratio feedback control is performed based on the output signal of the oxygen sensor in order to control the air-fuel ratio to the stoichiometric air-fuel ratio point at which the exhaust gas purification rate is high.

When the oxygen sensor used for this air-fuel ratio feedback control does not function properly, exhaust gas emissions may worsen, so various techniques have been proposed to diagnose abnormalities in the oxygen sensor. Japanese Unexamined Patent Publication 1986
-151770 Public Shoes (Refer to Japanese Patent Application Laid-Open No. 53-95421). [Problems to be Solved by the Invention] However, when the oxygen sensor is poisoned by various substances, the sensor output shifts to lean or rich and the characteristics change, as shown in Figure 13. As a result, air-fuel ratio feedback control based on the output signal of the oxygen sensor may not be performed properly.
There is a problem that emissions deteriorate.4 For example, when air-fuel ratio feedback control is performed using an oxygen sensor poisoned with silicon, etc., NO
When x increases and air-fuel ratio feedback control is performed using an oxygen sensor poisoned by lead or the like, there is a problem that C○ in the exhaust gas increases.The present invention solves the above problems. The purpose of this invention is to provide an abnormality detection device that accurately detects abnormalities in oxygen sensors.

[Means for solving the problem] Claim 1 of the present invention made to solve the above problem
Abnormality Detection Device for Oxygen Sensor (Ambition) As shown in FIG. an air-fuel ratio setting means M3 that sets the air-fuel ratio of the fuel mixture to a lean or rich state by open-loop control; and an output signal of the oxygen sensor M2 when the air-fuel ratio is set to a lean state by the air-fuel ratio setting means M3. is above a predetermined threshold value, or when the output signal of the oxygen sensor M2 is below a predetermined threshold value when the air-fuel ratio is set rich, an abnormality determining means M4 determines that there is an abnormality in the oxygen sensor M2. The main point is that it has the following.

Further, an abnormality detection device for an oxygen sensor according to claim 2 {as illustrated in FIG. The air-fuel ratio setting means M7 sets the air-fuel ratio of the fuel mixture supplied to the internal combustion engine M5 to lean and rich states by open loop control, and the air-fuel ratio setting means M7 sets the air-fuel ratio to lean and rich. an extreme value detection means M8 that detects the minimum value and maximum value of the output signal of the oxygen sensor M6 when The present invention further comprises an abnormality determining means M9 that determines that there is an abnormality in the oxygen sensor M6 when the oxygen sensor M6 is within the range of .

Furthermore, an abnormality detection device for an oxygen sensor according to a third aspect of the present invention is, as illustrated in FIG. an air-fuel ratio control means M12 that performs feedback control of the air-fuel ratio based on the output signal of the oxygen sensor M11; and when the air-fuel ratio control means M12 performs feedback control of the air-fuel ratio, the output signal of the oxygen sensor M11 is Abnormality determination means M1 that determines that there is an abnormality in the oxygen sensor M11 when the output value is within a predetermined range;
The main point is that it has the following.

Here, the minimum value and the maximum value may each be determined from the average value of multiple times.

Furthermore, the oven lube control does not involve feedback control of the air-fuel ratio of the fuel mixture based on the output signal of the oxygen sensor, but simply refers to control that switches and sets the air-fuel ratio to a lean or rich state. .

[Function] The oxygen sensor abnormality detection device according to claim 1: The air-fuel ratio setting means M3 performs open loop control on the air-fuel ratio of the fuel mixture supplied to the internal combustion engine M, so that the air-fuel ratio is in a lean or rich state. Set to . If the output signal of the oxygen sensor M2 exceeds a predetermined threshold value when the air-fuel ratio is set to lean, the abnormality determining means M4 determines that there is an abnormality in the oxygen sensor M2. Alternatively, if the output signal of the oxygen sensor M2 becomes below a predetermined threshold value when the air-fuel ratio is set to a rich level, the abnormality determining means M4 determines that there is an abnormality in the oxygen sensor M2, as described above.

The oxygen sensor abnormality detection device according to claim 2 also includes an air-fuel ratio setting means M7 that performs open loop control on the air-fuel ratio of the fuel mixture supplied to the internal combustion engine M5 to switch the air-fuel ratio between lean and rich states. and set it. Then, the extreme value detection means M8 detects the minimum value and maximum value of the output signal of the oxygen sensor M6 when the air-fuel ratio is set to lean or rich. Here, if at least one of the local minimum value or the local maximum value is within the predetermined output value range, E f&
The abnormality determining means M9 determines that there is an abnormality in the acid poison sensor M6.

Further, in the oxygen sensor abnormality detection device according to the third aspect, the air-fuel ratio control means M12 performs feedback control of the air-fuel ratio based on the output signal of the oxygen sensor M1. and,
When this air-fuel ratio feedback control is being performed,
When the output signal of the oxygen sensor M1 is within a predetermined output value range, the abnormality determining means M13 determines that there is an abnormality in the oxygen sensor M11.

Next, two principles of the abnormality detection device for each of the oxygen sensors will be explained by giving an example of each invention.

■ An abnormality detection device for an oxygen sensor according to claim 1 As shown in FIG.
3) to rich (e.g., λ=0.97), the output signal of the oxygen sensor changes to the first threshold value Vt (e.g., 30
0 mV) and the second threshold V2 (for example, 7
This results in an output with a large amplitude exceeding 00 mV).

However, oxygen sensors poisoned by silicone etc.
That is, when air-fuel ratio feed pack control is performed based on the output, the oxygen sensor IL increases NOx emissions. When the air-fuel ratio is lean, the output signal (voltage) becomes higher than that of a normal oxygen sensor. On the other hand, an oxygen sensor poisoned by lead or the like, i.e. oxygen sensor 1 whose output increases when the same control as described above is performed, is a normal oxygen sensor when the air-fuel ratio is rich. The output signal (voltage) is lower in comparison.

Therefore, if the output signal of the oxygen sensor exceeds a predetermined threshold when the air-fuel ratio is set to lean, it can be determined that the oxygen sensor is a deteriorated sensor that emits a large amount of NOx; If the output signal of the oxygen sensor becomes 12 below the predetermined threshold when 12 is set to rich, f1
It can be determined that the oxygen sensor is a deteriorated sensor that emits a large amount of C○.

■Abnormality Detection Device for Oxygen Sensor of Claim 2 As shown in FIG. The amplitude of the output signal becomes large, and the minimum value of the output signal is less than the first threshold value v1, and the maximum value of the output signal exceeds the second threshold value v2.

However, the output signal of the oxygen sensor whose NOx emission amount increases has a high voltage level and oscillates with a small amplitude around the second threshold value v2. On the other hand, the output signal of the oxygen sensor increases the amount of C○ discharge {the voltage level elsewhere is low,
It vibrates with a small amplitude near the first threshold value v1.

Therefore, for either the minimum value or the maximum value of the output signal of the oxygen sensor, for example, the first threshold value V and the second threshold value V
By determining that there is an abnormality in the oxygen sensor when the oxygen sensor is within a predetermined range between 2 and 2, it is possible to detect an abnormality in the oxygen sensor.

(2) Abnormality Detection Device for Oxygen Sensor According to Claim 3 As shown in FIG. 6, when the oxygen sensor is in good condition and the feedback control is performed to increase the air-fuel ratio by 1, the amplitude of the output signal of the oxygen sensor becomes large.

However, when feedback control of the air-fuel ratio is performed using an oxygen sensor that increases NOx emissions or an oxygen sensor that increases C○ emissions, the output signal is sliced and has a small amplitude near bell V8. It becomes a thing.

Therefore, the output signal of the oxygen sensor is at the slice level vI
] By determining that there is an abnormality in the oxygen sensor when it is within a predetermined nearby range, it is possible to detect an abnormality in the oxygen sensor.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 7 is a system configuration diagram of the oxygen sensor abnormality detection device of the first embodiment.

As shown in the figure, the oxygen sensor abnormality detection device 1
It includes an electronic control unit (hereinafter simply referred to as ECU) 3 that detects the state of the engine 2 and performs various controls such as the air-fuel ratio and processes such as abnormality diagnosis.

The engine 2 has a combustion chamber 7 composed of a cylinder 4, a piston 5, and a cylinder head 6, and an ignition plug 8 is disposed in the combustion chamber 7.

Intake system of engine 2 {intake valve 9, intake port 10, intake pipe 11. It is comprised of a surge tank 12 that absorbs pulsation of intake air, a throttle valve 14 that adjusts the amount of intake air, and an air cleaner 15.

The exhaust system of the engine 2 (exhaust valve 16, exhaust port 17, exhaust manifold) 8 is composed of a catalytic converter 19 filled with a three-way catalyst, and an exhaust pipe 20.

The ignition system of the engine 2 consists of an igniter 2 that outputs the high voltage necessary for ignition, and a distributor 22 that distributes and supplies the high voltage generated by the igniter 21 to the ignition plug 8 in conjunction with a crankshaft (not shown). ing.

The fuel system of the engine 2 (top) consists of an electromagnetic fuel injection valve 25 that injects fuel from a fuel tank (not shown) into the vicinity of the intake port 10.

In addition, as a sensor for detecting the operating state of the engine 2,
An intake pressure sensor 31 that detects the pressure of intake air, an intake temperature sensor 32 that detects the temperature of intake air, and a throttle position sensor 33 that detects the opening degree of the throttle valve 14.
, a water temperature sensor 35 that detects the temperature of the cooling water, and a catalytic converter] A downstream oxygen sensor 37 (hereinafter referred to as a sub-oxygen sensor, but this sensor is installed as necessary) detects the oxygen concentration of the distributor 22, a cylinder discrimination sensor 38 that outputs a reference signal every revolution of the camshaft of the distributor 22, 22
The rotation speed sensor 39 outputs a rotation angle signal every 1/24 rotation of the camshaft.

The detection signals from each of the sensors are input to the ECU 3, and the rotational speed, air-fuel ratio, etc. of the engine 2 are controlled based on the signals. ECU3 is the well-known CPLJ3 a, ROM
3 b, RAM3 c, backup RAM
3d, the circuit is configured as a logic operation circuit centering on the timer 3e.It is connected to the input/output board 3g via the common bus 3f, and performs input/output with the outside. The CPU 3a inputs detection signals from the intake pressure sensor 31, intake temperature sensor 32, throttle position sensor 33, water temperature sensor 35, oxygen sensor 36, and sub oxygen sensor 37 via the A/D converter 3h and the input/output port 3g. do. In addition, the detection signals of the cylinder discrimination sensor 38 and the rotation speed sensor 39 are transferred to the waveform shaping circuit 31.
and input via the input/output port 3g. On the other hand, CPU
3a drives and controls the igniter 21, the fuel injection valve 25, a check lamp 40 that indicates an abnormality in the oxygen sensor 36, etc. via the input/output port 1-3g and the drive circuit 3m.

The backup RAM 3d of the ECU 30 is configured such that power is supplied through a route that does not involve an ignition switch (not shown) and that various data and the like are held regardless of the state of the ignition switch.

Next, each process for detecting an abnormality in the oxygen sensor 36 executed by the ECU 3 will be sequentially explained.

[1] Processing of First Embodiment First, based on the flowchart of FIG. 8, a process of detecting a sensor that is poisoned by a cypress or the like and whose N○X increases during feedback control will be described. This process is performed with the engine 2 warmed up.

First, a process is performed to stop feedback control of the air-fuel ratio (step 100). Then, in a state where this feedback control is stopped, that is, by open loop control, a process is performed in which the fuel injection valve 25 is drive-controlled to set the air-fuel ratio to a lean state (step 110). That is, the opening time of the fuel injection valve 25 is reduced, the air-fuel ratio is set to a lean state of λ=1.03, for example, and this state is maintained for a predetermined period of time. Then, the output signal of the oxygen sensor 36 at this time is detected (step 12o), and if the output signal of the oxygen sensor 36 is equal to or higher than a predetermined threshold value V3 (for example, 300 mV), the oxygen sensor 36 is poisoned by silicon or the like. TeN
It is determined that the sensor increases Ox emission (step 13o), and the check lamp 40 is turned on (step 1).
4o), temporarily end this process.

By performing such processing, it is possible to easily detect a sensor whose NOx emission increases.

[2] Processing of Second Embodiment Next, based on the flowchart of FIG. 9, a process for detecting a sensor whose emission of C○ increases due to poisoning with lead or the like will be described. The hardware configuration in the second embodiment below is the same as the configuration in the first embodiment described above.

First, similar to the process described above, a process is performed to stop feedback control of the air-fuel ratio (step 200).

Then, by open loop control, the fuel injection valve 25
A process is performed in which the air-fuel ratio is set to a rich state by driving and controlling the air-fuel ratio (step 210). That is, the valve opening time of the fuel injection valve 25 is increased, and the air-fuel ratio is set to a rich state of λ=0.97, for example, and this state is maintained for a predetermined time.

Then, the output signal E of the oxygen sensor 36 at this time is detected (
Step 220), when the output signal of the oxygen sensor 36 is less than a predetermined threshold value V4 (for example, 700 mV), it is determined that the oxygen sensor 36 is a sensor that is poisoned by lead or the like and increases the emission of C○ ( Step 23o), the check lamp 40 is turned on (step 24o), and the process is temporarily terminated.

By performing such processing, it is possible to easily detect one sensor color in which the emission of C○ increases.

[3] Processing of the third embodiment Next, based on the flowchart of FIG. 10, the minimum and maximum values of the output signal of the oxygen sensor 36 indicate that the oxygen sensor 36 has deteriorated due to being poisoned by silicon, lead, etc. The process of determining whether the item is real or not will be explained.

First, similar to the process described above, a process is performed to stop feedback control of the air-fuel ratio (step 300).

Then, by open-lube control, the fuel injection valve 25
A process is performed in which the air-fuel ratio is periodically switched between rich and lean states by driving and controlling the air-fuel ratio (step 310). That is, by adjusting the opening time of the fuel injection valve 250, the air-fuel ratio is set to λ=0 at a cycle of, for example, two ports. 97 rich state and λ=
7.03 Periodically switch to the No. 1 state. Then, the output signal of the oxygen sensor 36 at this time is detected (step 320), and a process of determining the minimum value and maximum value of the output signal is performed (step 330). Next, oxygen sensor 3
It is determined whether either the minimum value or the maximum value of the output signal No. 6 is within a predetermined output value range. That is, as shown in FIG. 5, if the local minimum value is greater than or equal to the first threshold value V (step 340) or if the local maximum value is less than or equal to the second threshold value v2 (step 350), this oxygen sensor 36 is It is determined that the deterioration is caused by poison, and the check lamp 40 is turned on (step 360), and the process is temporarily terminated.

By performing such processing, a sensor deteriorated due to poisoning can be easily detected.

[4] Processing of the fourth embodiment Next, regarding the process of determining whether or not the oxygen sensor 36 has been poisoned and deteriorated based on the output signal of the oxygen sensor 36 based on the flowchart of FIG. explain. Note that this process (different from the above-mentioned process) is a process for detecting an abnormality in the oxygen sensor 36 while the air-fuel ratio feedback process is being performed.

First, while air-fuel ratio feedback control is being executed, a process is performed to detect the output signal of the oxygen sensor 36 (
Step 400). Then, the minimum value and maximum value of the detected output signal are determined (step 410), and it is determined whether these values are within a predetermined narrow output value range with the slice level VB in between. That is, as shown in FIG. 6, the minimum value is the slice level vl! is greater than or equal to the smaller threshold vL (step 420), and the maximum value is further sliced to a threshold V. ．． If it is less than 1 (step 430), it is determined that the oxygen sensor 36 has deteriorated due to poisoning, the check lamp 40 is turned on (step 440), and the process is temporarily terminated.

The abnormality detection process of the oxygen sensor 36 in the above embodiment may be performed, for example, when a vehicle equipped with this oxygen sensor 36 stops at a traffic light, or during a check such as an inspection at a factory, etc. It's okay.

Next, the above-mentioned processes are performed to actually make the oxygen sensor 36
In each of the following experiments, which describe experimental examples in which abnormalities were detected, a good oxygen sensor 36 or a deteriorated oxygen sensor 36 was installed in the vehicle's exhaust system, and conditions such as engine speed and air-fuel ratio were changed. , and detect the output signal at that time (Experiment Example 1) Using oxygen sensors 36 with different NOx emissions, set the air-fuel ratio to a lean state, and further change the engine speed to adjust the output signal of the oxygen sensor 36. The voltage of the output signal was measured. The experimental conditions and results are shown in Table 1. In this table,
A and B show different car models equipped with the oxygen sensor 36, and C and D show different experimental conditions. That is, the experimental conditions for C are high exhaust gas flow velocity, engine speed 150 Ortq, excess air ratio λ = 1.04, and D
The flow velocity is slow, the engine rotation speed is 800 rpm,
It shows λ=1.03. Further, sample floors 1 and 2 are good sensors, and samples N03 to 5 are deteriorated sensors with a large amount of NOx. In addition, each experimental result shows the average value of three measurements.

Table 1 As is clear from Table 1, the sensor output is small when the air-fuel ratio is lean regardless of the engine speed, but the sensor output is small when the air-fuel ratio is lean, regardless of the engine speed.
In the deteriorated sensor No. 5, the sensor output is large. Therefore, by making a determination using a predetermined threshold value (for example, 300 mV), it is possible to easily detect a deteriorated sensor that emits a large amount of NOx.

The conditions for this experiment are preferably within the range of conditions shown in Table 2 below, for example.

Table 2 Table 3 (Experiment Example 2) Using oxygen sensors 36 with different C○ emissions, set the air-fuel ratio to a rich state, and measure the voltage of the output signal of the oxygen sensor 36 in the same manner as above. The experimental conditions and results are shown in Table 3. In this table, A and B are the same as above, but the air-fuel ratio of C and D is rich (λ=0.
97).

In addition, samples Nllll1 and Nllll2 are good sensors, and sample NC
13 to 4 are deteriorated sensors with a large number of C○.

As is clear from Table 3, the sensor output in the condition where the air-fuel ratio is rich is greater than 1 in the good sensors of samples Ncl~2, but the sensor output is small in the degraded sensors of samples Nllll3~4. Therefore, the predetermined threshold (
For example, by making the determination at 700 mV), it is possible to easily detect a degraded sensor that emits a large amount of C○.

Ugly The conditions for this experiment are preferably within the range of conditions shown in Table 4 below.

Table 4 3 to 5 are deterioration sensors.

Table 5 (Experimental Example 3) In this experimental example, unlike the previous experimental example, the experiment was conducted by periodically switching the air-fuel ratio between lean and rich states.
In other words, a good sensor or N
Using an oxygen sensor 36 that emits a large amount of O x or CO, the minimum and maximum values of the voltage of the output signal of the oxygen sensor 36 are measured. The experimental conditions and results are shown in Table 5 (NO.
x measurement results) and Table 6 (Co measurement results).

Here, the engine speeds at C and D are the same as in Experimental Example 1, and the excess air ratio (λ) and switching period (Hz) in both tables are the same. Further, in both tables, sample Ncl~2 is a good sensor, and in Table 6 of the sample level, the conditions for this experiment are preferably within the range of conditions as shown in Table 7 below, for example.

Table 7 As is clear from Tables 5 and 6, sample Nll
The range of sensor output is large when the air-fuel ratio is lean and rich, but sample Nn3
The width of the sensor output is small in the deteriorated sensors of 5 to 5. Therefore, two predetermined upper and lower thresholds (for example, the lower one is 3
By making the determination at 0.0 mV and 700 mV at the higher end, it is possible to easily detect both degraded sensors that emit a large amount of N○X and CO.

(Experimental example 4) In this experimental example (above), the experiment was conducted with feedback control of the air-fuel ratio instead of open-loop control as in the previous experimental example. In other words, the same good sensor as used in experimental examples 1 to 3 was used. Feedback control of the air-fuel ratio is performed using an oxygen sensor 36 that emits a large amount of NOx or CO.
Minimum value of the voltage of the output signal of the oxygen sensor 36 (when lean)
The experimental conditions and results for measuring the maximum value (when rich) are shown in Table 8 (measurement results of NOx) and Table 9 (measurement results of CO). Here, C and D indicate the experimental conditions when vehicle A was driven at a constant speed. Also, in both tables, samples Nl111-2 are good sensors, and sample NC
L3 and L4 are deterioration sensors.

Table 8 Table 9 As is clear from Table 8 and Table 9, sample Nct
The width of the sensor output (difference between the maximum value and the minimum value) is large for the good sensors 1 and 2 when the air-fuel ratio is lean and rich, but the width of the sensor output is small for the degraded sensors of samples NC13 to 4. It has become.

Therefore, by making a determination using two predetermined upper and lower threshold values VL and Vl+ (for example, 250 mV for the lower one and 850 mV for the higher one), it is possible to easily detect both degraded sensors that emit a large amount of NOx and CO.

It goes without saying that the present invention is not limited to the above embodiments, but can be implemented in various forms within the scope of the present invention.

For example, in the embodiment described above, deterioration of the oxygen sensor 36 was detected, but the present invention can also be applied to detect deterioration of the sub-oxygen sensor 37.

[Effects of the Invention] As explained above, the oxygen sensor abnormality detection device (1) according to claim 1. If the output signal of the oxygen sensor is equal to or higher than a predetermined threshold when the air-fuel ratio is set to lean by open loop control. , or if the output signal of the oxygen sensor is below a predetermined threshold when the air-fuel ratio is set to rich, it is determined that there is an abnormality in the oxygen sensor. When used for feedback control, a deteriorated oxygen sensor that increases NOx or C○ can be easily and reliably detected.

Further, the abnormality detection device for an oxygen sensor according to claim 2, detects the minimum value and maximum value of the output signal of the oxygen sensor when the air-fuel ratio is set to lean and rich by open loop control, and If at least one of the maximum values is within a predetermined output value range, it is determined that there is an abnormality in the oxygen sensor, so that a deteriorated oxygen sensor can be easily and reliably detected in the same manner as described above.

Furthermore, the oxygen sensor abnormality detection device in Item 3 performs feedback control of the air-fuel ratio, and if the output signal of the oxygen sensor at that time is within a predetermined output value range, it is determined that there is an abnormality in the oxygen sensor. Therefore, a deteriorated oxygen sensor can be easily and reliably detected in the same manner as described above.

[Brief explanation of drawings]

FIG. 1 is an illustration of the basic structure of the invention of claim 1, FIG. 2 is an illustration of the basic structure of the invention of claim 2, and FIG. 3 is an illustration of the basic structure of the invention of claim 3. FIG. 4 is an explanatory diagram illustrating the principle of the invention of claim 1, FIG. 5 is an explanatory diagram illustrating the principle of the invention of claim 2, FIG. 6 is an explanatory diagram illustrating the principle of the invention of claim 3, FIG. 7 is a system configuration of the first embodiment of the present invention, FIG. 8 is a flowchart showing the processing of the first embodiment, and FIG. 9 is a flowchart showing the processing of the second embodiment. FIG. 10 is the flowchart of the third embodiment. Flowchart showing the processing of 1st
Figure 1 is a flowchart showing the processing of the fourth embodiment;
The figure is a graph showing the relationship between air-fuel ratio and emissions.
FIG. 3 is a graph showing the relationship between the air-fuel ratio and the sensor output. Ml, MS, Ml○... Internal combustion engine M2, M6, Mll... Oxygen sensor M3, M7... Air-fuel ratio setting means M4. M9, M13...Abnormality determination means M8...Extreme value detection means M12...Air-fuel ratio control means 2...Internal combustion engine 3...Electronic control unit (ECU) 25...Fuel injection valve 36. ...Oxygen sensor 37...Sub oxygen sensor 4o...Check lamp

Claims (1)

[Scope of Claims] 1. A device for detecting an abnormality in an oxygen sensor that outputs a signal according to the oxygen concentration in exhaust gas of an internal combustion engine, comprising: controlling the air-fuel ratio of a fuel mixture supplied to the internal combustion engine by open-loop control. an air-fuel ratio setting means for setting the air-fuel ratio to a lean or rich state; Abnormality determination means for determining that there is an abnormality in the oxygen sensor if the output signal of the oxygen sensor is less than a predetermined threshold value when the oxygen sensor is set to rich; Device. 2. In a device for detecting an abnormality in an oxygen sensor that outputs a signal according to the oxygen concentration in exhaust gas of an internal combustion engine, the air-fuel ratio of the fuel mixture supplied to the internal combustion engine is set to a lean or rich state by open loop control. an air-fuel ratio setting means for detecting the minimum value and maximum value of the output signal of the oxygen sensor when the air-fuel ratio is set to lean and rich by the air-fuel ratio setting means; Abnormality determining means for determining that there is an abnormality in the oxygen sensor when at least one of the minimum value and maximum value detected by the value setting means is within a predetermined output value range; An abnormality detection device for an oxygen sensor, characterized by the following. 3. A device for detecting an abnormality in an oxygen sensor that outputs a signal according to the oxygen concentration in exhaust gas of an internal combustion engine, comprising: an air-fuel ratio control means that performs feedback control of an air-fuel ratio based on an output signal of the oxygen sensor; abnormality determination for determining that there is an abnormality in the oxygen sensor if the output signal of the oxygen sensor is within a predetermined output value range when feedback control of the air-fuel ratio is performed by the fuel ratio control means; An abnormality detection device for an oxygen sensor, comprising: means.